In the preparation of dispersants and additives incorporating amine reaction products for use in lubricants and fuels, unconsumed reactant amines and byproducts, in the form of alkenyl amines and the like are usually present. Even in minute quantities, these impurities adversely affect the performance of the dispersants or additives as well as causing a hazy cast in their appearance; often, an undesired coloration, and color-instability.
Illustrative of the adverse effects secured where these low molecular weight reactants and byproducts are permitted to remain in the dispersant is their tendency to form deposits about the lower piston skirts as reflected particularly by Caterpillar diesel engine tests.
Various means for removal of these undesired reactants and byproducts, occurring primarily in the form of alkenyl amines have been known heretofore, including high vacuum distillation, solvent extraction techniques and the like.
Use of the foregoing methods of separation involve substantial difficulties and the incurring of substantial liabilities, as for example, the need for elaborate equipment, low throughput, and substantial expense. In addition, the removal effected is often not complete and hence the elimination of engine deposits is not satisfactorily resolved.
The use of an inexpensive and simple technique has been described heretofore for application to the removal of phenolic materials from phenol-derived solutions in which polyurethane foam provides an adsorbent for the undesired phenolic materials but the application of this process to removal of amines and particularly alkenyl amines, often in extremely small amounts, from amine-based dispersants and additives has not been elucidated.
Thus, if polyurethane foams could be used in securing amine-based lubricants and additives free of low-molecular weight unreacted amines and amine byproducts, a significant advance in the state of the art would be achieved.